EP0764529A2 - Electrostatic ink-jet recording head - Google Patents
Electrostatic ink-jet recording head Download PDFInfo
- Publication number
- EP0764529A2 EP0764529A2 EP96250175A EP96250175A EP0764529A2 EP 0764529 A2 EP0764529 A2 EP 0764529A2 EP 96250175 A EP96250175 A EP 96250175A EP 96250175 A EP96250175 A EP 96250175A EP 0764529 A2 EP0764529 A2 EP 0764529A2
- Authority
- EP
- European Patent Office
- Prior art keywords
- ink
- tip end
- cover member
- recording
- base plate
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Granted
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Classifications
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B41—PRINTING; LINING MACHINES; TYPEWRITERS; STAMPS
- B41J—TYPEWRITERS; SELECTIVE PRINTING MECHANISMS, i.e. MECHANISMS PRINTING OTHERWISE THAN FROM A FORME; CORRECTION OF TYPOGRAPHICAL ERRORS
- B41J2/00—Typewriters or selective printing mechanisms characterised by the printing or marking process for which they are designed
- B41J2/005—Typewriters or selective printing mechanisms characterised by the printing or marking process for which they are designed characterised by bringing liquid or particles selectively into contact with a printing material
- B41J2/01—Ink jet
- B41J2/015—Ink jet characterised by the jet generation process
- B41J2/04—Ink jet characterised by the jet generation process generating single droplets or particles on demand
- B41J2/06—Ink jet characterised by the jet generation process generating single droplets or particles on demand by electric or magnetic field
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B41—PRINTING; LINING MACHINES; TYPEWRITERS; STAMPS
- B41J—TYPEWRITERS; SELECTIVE PRINTING MECHANISMS, i.e. MECHANISMS PRINTING OTHERWISE THAN FROM A FORME; CORRECTION OF TYPOGRAPHICAL ERRORS
- B41J2/00—Typewriters or selective printing mechanisms characterised by the printing or marking process for which they are designed
- B41J2/005—Typewriters or selective printing mechanisms characterised by the printing or marking process for which they are designed characterised by bringing liquid or particles selectively into contact with a printing material
- B41J2/01—Ink jet
- B41J2/015—Ink jet characterised by the jet generation process
- B41J2/04—Ink jet characterised by the jet generation process generating single droplets or particles on demand
- B41J2/06—Ink jet characterised by the jet generation process generating single droplets or particles on demand by electric or magnetic field
- B41J2002/061—Ejection by electric field of ink or of toner particles contained in ink
Definitions
- the present invention relates to an ink-jet recording head, and more particularly, to an electrostatic ink-jet recording head for ejecting ink particle by electrostatic forces to effect printing on a piece of recording paper.
- a non-impact recording method is superior in that an extremely small noise is generated during the printing.
- the ink-jet recording method is considered a very excellent recording because a high speed recording may be attained on a normal paper with a simple mechanism.
- a variety of methods therefor have heretofore been proposed.
- the ink-jet recording methods falls into the following categories: a method in which pressure waves are generated in an ink chamber by a piezoelectric element to thereby eject ink from a nozzle for recording, another method in which ink is ejected from a nozzle by bubbles generated by heat, and an electrostatic recording method.
- a method in which pressure waves are generated in an ink chamber by a piezoelectric element to thereby eject ink from a nozzle for recording another method in which ink is ejected from a nozzle by bubbles generated by heat
- an electrostatic recording method by which a size of ink droplets may readily be controlled will hereinafter be noticed.
- the electrostatic ink-jet recording apparatus is provided an opposite electrode disposed on a back side of the recording paper, and a ink-jet recording head for ejecting ink particle to the recording paper.
- the ink-jet print head has stylus electrodes confronting with an opposite electrode. A voltage is applied to the electrodes so that an electric field generated by the application causes the ink particle such as charged toner or the like to fly toward the opposite electrode.
- Fig. 1 is a schematic perspective view showing a conventional electrostatic ink-jet printing apparatus.
- a top surface of a base plate 52 of an ink-jet recording head 50 is covered by a cover 54.
- Slit-like ink ejection holes 55 for holding the ink are provided therein.
- a plurality of recording electrodes 53 are disposed in parallel along the ink emission direction. They are provided on the surface of the base plate 52. These recording electrodes 53 are connected to a voltage driving section (not shown). A high voltage pulse is applied selectively to the recording electrodes 53 during the printing.
- an opposite electrode 51 is disposed through the recording paper P on a line extending from the recording electrodes 53, thereby generating an electric field together with the recording electrodes 53 during the recording.
- the recording electrodes 53 are formed into styli, the electric field is concentrated on a tip end of each recording electrode 53, and charge is accumulated on the ink located near to the recording electrodes.
- the process for accumulation of the charge depends upon the kind of the ink. In case of conductive ink, the process depends upon the electrostatic induction and in case of inductive ink, the process depends upon induction polarization. Also, in case of ink in which color agent particle (charged toner) is dispersed in solution, the color particle itself has a nominal charge due to a Zeta potential so that a floating motion of the charged color particle is biased by the electric field generated with the opposite electrode.
- color agent particle charged toner
- any type of the above-described ink may be applied to the ink used in the electrostatic ink-jet recording apparatus.
- bleeding of the ink occurs on the recording paper, and feathering or color breed inherent in multi-color recording occurs, resulting in degradation in printing quality, disadvantageously.
- the bleeding degree depends upon the recording paper, the printing results are different in accordance with a difference of the paper.
- it takes a certain period of time for drying of ink there is a disadvantage that a recording speed is limited thereby.
- the ink in which color particle is dispersed is used and the color particle (charged toner) is ejected for recording, it is possible to carry out the recording without any bleeding of ink irrespective of the kind of the recording paper. For this reason, for the ink-jet recording apparatus shown in Fig. 1, it is preferable to use ink in which the color particle is dispersed.
- the color particle contained in the ink solution is subjected to a strong attractive force toward the opposite electrode 51 side in Fig. 1, i.e., in a direction toward the recording paper P by a Coulomb force generated by the charge accumulated by the recording electrodes 53. If the Coulomb force overcomes the surface tension of the ink, the ink is ejected to stick to the recording paper P. In this way, in response to an image to be recorded, a high voltage pulse is applied to the recording electrodes 53 to thereby carry out a desired recording operation.
- the conductivity or inductivity of the ink to be used for recording is larger than the conductivity or inductivity of air, a position where the electric field is concentrated is not only determined by the arrangement of the recording electrodes, but the shape of ink meniscus formed on the ink ejection port is affected.
- the ink meniscus is uniform in the longitudinal direction of the ink ejection ports.
- fine irregularity is formed on the surface of the ink meniscus due to the machining allowance of the opening portions, the vibration of the meniscus after the ink ejection, the natural swing of the meniscus, and the like.
- the electric field is concentrated on the convex portions of the fine corrugation of the meniscus generated in the vicinity of the recording electrode by the relationship of the conductivity and inductivity of the ink. Then, when the shape of the meniscus begins to be deformed by the Coulomb force, the concentration of the electric field is further promoted. As a result, the position where the ink flies is minutely displaced due to the irregularity of the fine meniscus in the initial stage. If this occurs, even if a high voltage pulse is applied to a certain recording electrode, the ink would fly from a position displaced from the recording electrode. As a result, there are cases where it would be impossible to carry out the recording on a desired position. This leads to degradation in printing quality.
- the electrostatic ink-jet recording head has convex portions 66 at a tip end position of the recording electrode 63 at a tip end portion of the base plate 62 as shown in Fig. 2.
- the convex and concave shapes corresponding to the shape of the convex portion 66 are applied to the ink meniscus formed in the vicinity of the tip ends of the recording electrodes 63.
- the electric field at the tip ends of the recording electrodes 63 is concentrated onto the convex portions 66.
- the charged color particle in the ink migrates toward the tip ends (tip ends of the convex portions 66) of the meniscus in accordance with the electric field in the ink to thereby first fly.
- the ink-jet recording head shown in Fig. 2 for example, in the case where the resolving power of the printer is set at 300 dpi, it is necessary to set up the arrangement pitch of the recording electrodes 63 to about 85 ⁇ m. Therefore, the fine convex and concave portions must be formed at the tip end of the base plate 62 corresponding to the recording electrodes having such a fine pitch. For this reason, the base plate material and the machining process are largely limited, causing an increased cost, disadvantageously. Also, in order to meet a sufficient mechanical strength of the base plate 62, the latter needs a thickness of 100 ⁇ m or more, whereas the pitch of the convex and concave portions to be machined must be one fifth or sixth of this thickness or less. Accordingly, the machining is extremely difficult, and also a cost for manufacture is increased, disadvantageously.
- Fig. 2 it is possible to form the base plate 62 of thin and soft material by providing a reinforcement plate 67 at a position where the recording electrodes 63 are partitioned.
- this degrades the mechanical strength of the convex portions of the tip end of the base plate. Accordingly, when the head tip portion is to be cleaned, or the recording paper is jammed, it is disadvantageous that it is likely that the convex portions of the tip end of the base plate is damaged.
- the direction of the electric field in the vicinity of the recording electrodes diverges (in directions indicated by arrows) from the recording electrodes as shown in Fig. 3, the migration of color particle does not occur toward the meniscus end on the axes of the recording electrodes or does not smoothly occur. As a result, the performance for the high speed and continuous ejection of the ink has to be improved to some extent.
- an object of the present invention is to provide an electrostatic ink-jet recording head which may readily be manufactured at low cost to thereby rapidly eject color particle in ink in a stable manner.
- an electrostatic ink-jet recording head which uses ink containing color particle charged with a predetermined polarity, comprising a base plate, at least one recording electrode formed on a surface thereof for generating an electric field for ink ejection; a cover member for forming an ink flow path in an ink ejection direction on the surface of said base plate where said recording electrode is formed; and an ink ejection port formed at an end portion of the ink flow path on the ink ejection side.
- At least one convex portion is formed at a tip end portion of said cover member on the ink ejection side, and a tip end portion of the convex portion is set to project in the ink ejection direction beyond the tip end portion of the base plate on the ink ejection side.
- the ink meniscus when the ink containing the color particle is filled in the ink flow path, the ink meniscus is formed along the shape of the convex portion of the cover member.
- the electric field is diverged from the recording electrode, it is concentrated on the tip end portion of the cover member along the shape of the surface of the ink meniscus due to the relationship of the conductivity and inductivity of the ink and air.
- the concentration of the electric field the color particle (charged toner) in the ink migrates toward the tip end of the meniscus and the color particle flies from the tip end of the cover member together with the ink solution.
- the convex portion of the cover member on the ink ejection side projects beyond the tip end portion of the base plate, the electric field from the tip end of the recording electrode concentrates to the meniscus on the tip end portion of the convex portion. It is therefore possible to rapidly supply color particle to the meniscus end portion, and to carry out the recording at a high speed with high precision.
- a plurality of stylus recording electrodes are arranged in parallel in a longitudinal direction along the ink ejection direction and a sawtoothed portion is formed on the ink ejection side of the cover member.
- the convex portions form convex portions of said sawtoothed portion, and the convex portions are arranged so as to overlap lines extending from the stylus recording electrodes.
- the convex ink meniscus is formed corresponding to the sawtoothed shape, the electric field diverged from the recording electrode concentrates on the tip end of the convex portion of the ink meniscus, and the color particle is effectively ejected from the tip end of the convex portion.
- an electrostatic ink-jet recording head includes a base plate 1, a plurality of recording electrodes 2 formed on a too surface of the base plate 1 for generating an electric field for the ink ejection, a cover member 4 for forming slit-like ink flow paths 3 in an ink ejection direction (indicated by arrow A) along the recording electrodes 2, and ink ejection ports 5 formed at a tip end portion on the ink ejection side of the slit-like ink flow paths 3.
- the tip end portion of the cover member 4 on the ink ejection side has a shape which projects beyond the tip end portion of the base plate 1 on the ink ejection side in the ink ejection direction.
- the recording electrodes 2 are formed into styli in the longitudinal direction along the ink ejection direction. Also, the tip end portion of the cover member 4 on the ink ejection side are formed into sawteeth. A plurality of convex portions 12 form the sawteeth having sharp-pointed ends, and they are arranged so as to overlap on a line extending from each stylus recording electrode 2.
- the base plate 1 is formed of insulating material such as glass.
- the recording electrodes 2 one formed by patterning through a photo-lithographic method after nickel, chromium or the like has been sputtered on a surface, on the cover member side, of the base plate 1.
- the recording electrodes 2 are arranged at 300 dpi, i.e., at an interval of about 85 ⁇ m. Also, as shown in Figs. 5 and 6, the tip end portion of each recording electrode 2 is covered by an insulating layer 6.
- the cover member 4 is formed by molding resin such as polysulphone or the like.
- the cover member 4 is mounted to face the base plate 1.
- slit-like ink flow paths 3 are formed inside of the cover member 4 and an ink 9 is contained in the ink flow path 3.
- the ink ejection ports 5 are formed at the tip end portion of the cover member 4.
- the ink ejection ports 5 are formed by thickening the cover member 4. In other words, the ink ejection ports 5 are narrowed portions of the ink flow paths 3.
- Three side walls of the cover member 4 form the side surface of the ink flow paths 3 and they are intimately contacted with the base plate 1. With this arrangement, the ink flow paths 3 are closed except for the ink ejection ports 5.
- the ink recirculation ports 7 are provided on the top surface of the cover member 4 and are connected to an ink cartridge (not shown) via a pair of tubes (not shown). Then, under the condition that vacuum pressure at about 1 cmH 2 0 is applied to the ink 9 in the ink flow paths 3, the ink recirculation is forcibly effected.
- the recording ink is of a type such that color fine particles (toner) made of thermoplastic resin color are dispersed in liquid of petroleum type organic solution (isoparaffin hydrocarbon) together with charge controlling agent.
- the color particle is a charged toner which has been nominally charged with a positive polarity by Zeta potential.
- a plurality of path separators 4a of the cover member 4 are formed at positions where the adjacent recording electrodes 2 are partitioned.
- the path separators 4a are arranged so as to be in contact with the insulating layer 6 provided on the base plate 1 between the convex portions 12 of the cover member 4.
- an ink meniscus 8 is formed on the ink 9 at each ink ejection port 5 by the surface tension.
- the negative pressure is applied to the ink 9 within the ink flow path 3, and also, the tip end portions of the convex portions 12 at the tip end of the cover member 4 project beyond the tip end of the base plate 1 in the ink ejection direction.
- the ink meniscus 8 takes a concave surface shape slanted upwardly with an apex at the convex portion 12 as viewed from the side in Fig. 6. Furthermore, the ink meniscus 8 projects along the convex portion 12 as viewed from above as shown in Fig. 5.
- the electric field is formed from the recording electrode 2 to the opposite electrode (not shown) (corresponding to the opposite electrode 51 in Fig. 1), i.e., toward the recording paper.
- the direction of the electric field in the vicinity of the tip end of the recording electrode 2 is such that it diverges from the recording electrode 2.
- the charged toner in the ink 9 migrates in the ink along the electric field. As shown by the arrow in Fig. 8, a part of charged toner migrates directly toward the tip end portion of the meniscus 8. Also, another part of charged toner first migrates toward the ink meniscus surface and thereafter migrates to the meniscus end portion along the surface shape of the meniscus 8.
- the charged toner which has been concentrated on the tip end portion of the meniscus 8 is drawn by the strong electric field concentrated on the tip end portion of the meniscus and, as shown in Fig. 5, becomes a charged toner group 10 containing the ink solution to fly toward the opposite electrode (not shown), i.e., the recording paper to thereby perform the recording.
- the toner sticking on the recording paper to form the recording dots is heated by a heater (not shown) and fixed.
- the charge corresponding to the amount of charge held in the charged toner group 10 which has flown is supplied to the ink 9 in the vicinity of the ink ejection part 5 from the portion which is not covered by the insulating layer 6 of the recording electrode 2.
- the electric balance is always kept.
- the ink meniscus 8 projects along the convex portion 12 as shown in Fig. 5.
- the component in the tangent direction of the electric field with the meniscus 8 is toward the tip end of the meniscus 8 and its component becomes large. Accordingly, it is possible to rapidly supply the meniscus tip end portion with charged toner and to carry out high speed recording with high precision.
- the tip end portion of the cover member 4 is formed in the sawteeth, and the position of the convex portion 12 for forming the sawteeth is overlapped with a line extending from the stylus recording electrode 2.
- the ink meniscus 8 has an apex corresponding to the convex portion 12 of the cover member 4. For this reason, it is possible to more effectively concentrate the electric field diverging from the recording electrode 2 onto the convex portion 12, and to rapidly carry out the supply of the charged toner to the tip end portion of the meniscus. At the same time, it is possible to carry out the high speed printing with high precision by using the plurality of recording electrodes 2.
- the sawtoothed portion for concentration of the electric field is formed not on the base plate 1 but on the cover member 4, it is possible to widen the variety of selection of the base plate material. Also, it is possible to widen the freedom of selection of the formation process for the recording electrode arranged on the base plate 1 with high precision. As a result, by selecting the low cost material which would not be suitable in the conventional example due to the machining problem and using an easy process, it is possible to reduce the manufacture cost. Moreover, the thickness of the plate of the cover member 4 is made to one which is suitable for machining, it is possible to facilitate the machining of the sawtoothed portion, to thereby further reduce the manufacture cost.
- the cover member 4 is made of moldable material, it is possible to impart sufficient mechanical strength to the sawtoothed portion formed at the tip end portion on the ink ejection side. Thus, it is possible to prevent the damage of the sawtoothed irregularity portion due to the cleaning of the head tip portion and the clogging of the ports.
- the dielectric strength between the recording electrode 2 and the opposite electrode may be increased, and it is possible to effectively avoid such a disadvantage that an excessive current would flow due to the generation of jamming of the recording paper or the like to damage the drive device or the like.
- the cover member 4 may be made of other material. Also, for the electrostatic ink-jet recording head in accordance with the embodiment, the insulating layer 6 is formed after the recording electrode 2 has been printed first on the surface of the base plate 1, and thereafter, the cover member 4 which is separately machined is mounted on the base plate 1. Such an order of the manufacture process is preferable.
Abstract
Description
- The present invention relates to an ink-jet recording head, and more particularly, to an electrostatic ink-jet recording head for ejecting ink particle by electrostatic forces to effect printing on a piece of recording paper.
- A non-impact recording method is superior in that an extremely small noise is generated during the printing. In particular, the ink-jet recording method is considered a very excellent recording because a high speed recording may be attained on a normal paper with a simple mechanism. A variety of methods therefor have heretofore been proposed.
- The ink-jet recording methods falls into the following categories: a method in which pressure waves are generated in an ink chamber by a piezoelectric element to thereby eject ink from a nozzle for recording, another method in which ink is ejected from a nozzle by bubbles generated by heat, and an electrostatic recording method. Of these methods, the electrostatic recording method by which a size of ink droplets may readily be controlled will hereinafter be noticed.
- The electrostatic ink-jet recording apparatus is provided an opposite electrode disposed on a back side of the recording paper, and a ink-jet recording head for ejecting ink particle to the recording paper. The ink-jet print head has stylus electrodes confronting with an opposite electrode. A voltage is applied to the electrodes so that an electric field generated by the application causes the ink particle such as charged toner or the like to fly toward the opposite electrode.
- Fig. 1 is a schematic perspective view showing a conventional electrostatic ink-jet printing apparatus. In Fig. 1, a top surface of a
base plate 52 of an ink-jet recording head 50 is covered by acover 54. Slit-likeink ejection holes 55 for holding the ink are provided therein. Also, a plurality ofrecording electrodes 53 are disposed in parallel along the ink emission direction. They are provided on the surface of thebase plate 52. Theserecording electrodes 53 are connected to a voltage driving section (not shown). A high voltage pulse is applied selectively to therecording electrodes 53 during the printing. On the other hand, anopposite electrode 51 is disposed through the recording paper P on a line extending from therecording electrodes 53, thereby generating an electric field together with therecording electrodes 53 during the recording. - Here, since the
recording electrodes 53 are formed into styli, the electric field is concentrated on a tip end of eachrecording electrode 53, and charge is accumulated on the ink located near to the recording electrodes. - The process for accumulation of the charge depends upon the kind of the ink. In case of conductive ink, the process depends upon the electrostatic induction and in case of inductive ink, the process depends upon induction polarization. Also, in case of ink in which color agent particle (charged toner) is dispersed in solution, the color particle itself has a nominal charge due to a Zeta potential so that a floating motion of the charged color particle is biased by the electric field generated with the opposite electrode.
- Any type of the above-described ink may be applied to the ink used in the electrostatic ink-jet recording apparatus. However, in the recording depending upon the ejection of the ink per se, bleeding of the ink occurs on the recording paper, and feathering or color breed inherent in multi-color recording occurs, resulting in degradation in printing quality, disadvantageously. In this case, since the bleeding degree depends upon the recording paper, the printing results are different in accordance with a difference of the paper. Furthermore, since it takes a certain period of time for drying of ink, there is a disadvantage that a recording speed is limited thereby. However, if the ink in which color particle is dispersed is used and the color particle (charged toner) is ejected for recording, it is possible to carry out the recording without any bleeding of ink irrespective of the kind of the recording paper. For this reason, for the ink-jet recording apparatus shown in Fig. 1, it is preferable to use ink in which the color particle is dispersed.
- The color particle contained in the ink solution is subjected to a strong attractive force toward the
opposite electrode 51 side in Fig. 1, i.e., in a direction toward the recording paper P by a Coulomb force generated by the charge accumulated by therecording electrodes 53. If the Coulomb force overcomes the surface tension of the ink, the ink is ejected to stick to the recording paper P. In this way, in response to an image to be recorded, a high voltage pulse is applied to therecording electrodes 53 to thereby carry out a desired recording operation. - However, since the conductivity or inductivity of the ink to be used for recording is larger than the conductivity or inductivity of air, a position where the electric field is concentrated is not only determined by the arrangement of the recording electrodes, but the shape of ink meniscus formed on the ink ejection port is affected. In the ink-
jet recording head 50 shown in Fig. 1, it is preferable that the ink meniscus is uniform in the longitudinal direction of the ink ejection ports. However, actually, fine irregularity is formed on the surface of the ink meniscus due to the machining allowance of the opening portions, the vibration of the meniscus after the ink ejection, the natural swing of the meniscus, and the like. - In this case, the electric field is concentrated on the convex portions of the fine corrugation of the meniscus generated in the vicinity of the recording electrode by the relationship of the conductivity and inductivity of the ink. Then, when the shape of the meniscus begins to be deformed by the Coulomb force, the concentration of the electric field is further promoted. As a result, the position where the ink flies is minutely displaced due to the irregularity of the fine meniscus in the initial stage. If this occurs, even if a high voltage pulse is applied to a certain recording electrode, the ink would fly from a position displaced from the recording electrode. As a result, there are cases where it would be impossible to carry out the recording on a desired position. This leads to degradation in printing quality.
- On the other hand, Japanese Patent Application Laid-Open No. Sho 60-228162 laid open on November 13, 1986 discloses an example of countermeasure for the above described problem. In this publication, the electrostatic ink-jet recording head has convex
portions 66 at a tip end position of therecording electrode 63 at a tip end portion of thebase plate 62 as shown in Fig. 2. Thus, the convex and concave shapes corresponding to the shape of theconvex portion 66 are applied to the ink meniscus formed in the vicinity of the tip ends of therecording electrodes 63. Also, the electric field at the tip ends of therecording electrodes 63 is concentrated onto theconvex portions 66. As a result, in the case where the ink containing color particle is used, the charged color particle in the ink migrates toward the tip ends (tip ends of the convex portions 66) of the meniscus in accordance with the electric field in the ink to thereby first fly. - However, in the ink-jet recording head shown in Fig. 2, for example, in the case where the resolving power of the printer is set at 300 dpi, it is necessary to set up the arrangement pitch of the
recording electrodes 63 to about 85 µm. Therefore, the fine convex and concave portions must be formed at the tip end of thebase plate 62 corresponding to the recording electrodes having such a fine pitch. For this reason, the base plate material and the machining process are largely limited, causing an increased cost, disadvantageously. Also, in order to meet a sufficient mechanical strength of thebase plate 62, the latter needs a thickness of 100 µm or more, whereas the pitch of the convex and concave portions to be machined must be one fifth or sixth of this thickness or less. Accordingly, the machining is extremely difficult, and also a cost for manufacture is increased, disadvantageously. - In Fig. 2, it is possible to form the
base plate 62 of thin and soft material by providing areinforcement plate 67 at a position where therecording electrodes 63 are partitioned. However, this degrades the mechanical strength of the convex portions of the tip end of the base plate. Accordingly, when the head tip portion is to be cleaned, or the recording paper is jammed, it is disadvantageous that it is likely that the convex portions of the tip end of the base plate is damaged. - Furthermore, since the direction of the electric field in the vicinity of the recording electrodes diverges (in directions indicated by arrows) from the recording electrodes as shown in Fig. 3, the migration of color particle does not occur toward the meniscus end on the axes of the recording electrodes or does not smoothly occur. As a result, the performance for the high speed and continuous ejection of the ink has to be improved to some extent.
- In order to overcome defects inherent in the conventional technology, an object of the present invention is to provide an electrostatic ink-jet recording head which may readily be manufactured at low cost to thereby rapidly eject color particle in ink in a stable manner.
- According to the present invention, there is provided an electrostatic ink-jet recording head which uses ink containing color particle charged with a predetermined polarity, comprising a base plate, at least one recording electrode formed on a surface thereof for generating an electric field for ink ejection; a cover member for forming an ink flow path in an ink ejection direction on the surface of said base plate where said recording electrode is formed; and an ink ejection port formed at an end portion of the ink flow path on the ink ejection side. At least one convex portion is formed at a tip end portion of said cover member on the ink ejection side, and a tip end portion of the convex portion is set to project in the ink ejection direction beyond the tip end portion of the base plate on the ink ejection side.
- According to the present invention, when the ink containing the color particle is filled in the ink flow path, the ink meniscus is formed along the shape of the convex portion of the cover member. When the electric field is diverged from the recording electrode, it is concentrated on the tip end portion of the cover member along the shape of the surface of the ink meniscus due to the relationship of the conductivity and inductivity of the ink and air. By the concentration of the electric field, the color particle (charged toner) in the ink migrates toward the tip end of the meniscus and the color particle flies from the tip end of the cover member together with the ink solution.
- According to the present invention, since the convex portion of the cover member on the ink ejection side projects beyond the tip end portion of the base plate, the electric field from the tip end of the recording electrode concentrates to the meniscus on the tip end portion of the convex portion. It is therefore possible to rapidly supply color particle to the meniscus end portion, and to carry out the recording at a high speed with high precision.
- According to another aspect of the present invention, a plurality of stylus recording electrodes are arranged in parallel in a longitudinal direction along the ink ejection direction and a sawtoothed portion is formed on the ink ejection side of the cover member. The convex portions form convex portions of said sawtoothed portion, and the convex portions are arranged so as to overlap lines extending from the stylus recording electrodes.
- Thus, the convex ink meniscus is formed corresponding to the sawtoothed shape, the electric field diverged from the recording electrode concentrates on the tip end of the convex portion of the ink meniscus, and the color particle is effectively ejected from the tip end of the convex portion.
- In the accompanying drawings:
- Fig. 1 is a schematic perspective view showing a conventional electrostatic ink-jet recording apparatus;
- Fig. 2 is a perspective view showing another conventional electrostatic ink-jet recording apparatus;
- Fig. 3 is a schematic cross-sectional view showing a state of an electric field diverging from the recording electrode and a state of an ink meniscus formed at an ink ejection port in an electrostatic ink-jet recording head shown in Fig. 2;
- Fig. 4 is a perspective view showing an embodiment of an electrostatic ink-jet recording head according to the present invention;
- Fig. 5 is a partially fragmentary plan view of the ink-jet recording head shown in Fig. 4;
- Fig. 6 is a cross-sectional view taken along line C-C of Fig. 5;
- Fig. 7 is a cross-sectional view taken along line D-D of Fig. 5; and
- Fig. 8 is an enlarged cross-sectional view showing a part indicated by character B in Fig. 6.
- In Fig. 4 and Fig. 5, an electrostatic ink-jet recording head includes a
base plate 1, a plurality ofrecording electrodes 2 formed on a too surface of thebase plate 1 for generating an electric field for the ink ejection, a cover member 4 for forming slit-likeink flow paths 3 in an ink ejection direction (indicated by arrow A) along therecording electrodes 2, andink ejection ports 5 formed at a tip end portion on the ink ejection side of the slit-likeink flow paths 3. The tip end portion of the cover member 4 on the ink ejection side has a shape which projects beyond the tip end portion of thebase plate 1 on the ink ejection side in the ink ejection direction. - As shown in Fig. 5, the
recording electrodes 2 are formed into styli in the longitudinal direction along the ink ejection direction. Also, the tip end portion of the cover member 4 on the ink ejection side are formed into sawteeth. A plurality ofconvex portions 12 form the sawteeth having sharp-pointed ends, and they are arranged so as to overlap on a line extending from eachstylus recording electrode 2. - More specifically, the
base plate 1 is formed of insulating material such as glass. Therecording electrodes 2 one formed by patterning through a photo-lithographic method after nickel, chromium or the like has been sputtered on a surface, on the cover member side, of thebase plate 1. Therecording electrodes 2 are arranged at 300 dpi, i.e., at an interval of about 85 µm. Also, as shown in Figs. 5 and 6, the tip end portion of eachrecording electrode 2 is covered by an insulatinglayer 6. - The cover member 4 is formed by molding resin such as polysulphone or the like. The cover member 4 is mounted to face the
base plate 1. As shown in Fig. 6, slit-likeink flow paths 3 are formed inside of the cover member 4 and anink 9 is contained in theink flow path 3. Theink ejection ports 5 are formed at the tip end portion of the cover member 4. Theink ejection ports 5 are formed by thickening the cover member 4. In other words, theink ejection ports 5 are narrowed portions of theink flow paths 3. Three side walls of the cover member 4 form the side surface of theink flow paths 3 and they are intimately contacted with thebase plate 1. With this arrangement, theink flow paths 3 are closed except for theink ejection ports 5. Also, twoink recirculation ports 7 are provided on the top surface of the cover member 4 and are connected to an ink cartridge (not shown) via a pair of tubes (not shown). Then, under the condition that vacuum pressure at about 1 cmH20 is applied to theink 9 in theink flow paths 3, the ink recirculation is forcibly effected. Here it is preferable that the recording ink is of a type such that color fine particles (toner) made of thermoplastic resin color are dispersed in liquid of petroleum type organic solution (isoparaffin hydrocarbon) together with charge controlling agent. In this embodiment, the color particle is a charged toner which has been nominally charged with a positive polarity by Zeta potential. - As shown in Fig. 5 and Fig. 7, in the cover member 4, a plurality of
path separators 4a of the cover member 4 are formed at positions where theadjacent recording electrodes 2 are partitioned. Thepath separators 4a are arranged so as to be in contact with the insulatinglayer 6 provided on thebase plate 1 between theconvex portions 12 of the cover member 4. - The overall operation of the recording head according to the embodiment will now be described.
- When the
ink 9 is filled in theink flow paths 3 from theink recirculation port 7, as shown in Fig. 6, anink meniscus 8 is formed on theink 9 at eachink ejection port 5 by the surface tension. Here, the negative pressure is applied to theink 9 within theink flow path 3, and also, the tip end portions of theconvex portions 12 at the tip end of the cover member 4 project beyond the tip end of thebase plate 1 in the ink ejection direction. For this reason, theink meniscus 8 takes a concave surface shape slanted upwardly with an apex at theconvex portion 12 as viewed from the side in Fig. 6. Furthermore, theink meniscus 8 projects along theconvex portion 12 as viewed from above as shown in Fig. 5. - When a voltage pulse is applied to a desired
electrode 2 from a drive circuit (not shown), the electric field is formed from therecording electrode 2 to the opposite electrode (not shown) (corresponding to theopposite electrode 51 in Fig. 1), i.e., toward the recording paper. The direction of the electric field in the vicinity of the tip end of therecording electrode 2 is such that it diverges from therecording electrode 2. The charged toner in theink 9 migrates in the ink along the electric field. As shown by the arrow in Fig. 8, a part of charged toner migrates directly toward the tip end portion of themeniscus 8. Also, another part of charged toner first migrates toward the ink meniscus surface and thereafter migrates to the meniscus end portion along the surface shape of themeniscus 8. - The charged toner which has been concentrated on the tip end portion of the
meniscus 8 is drawn by the strong electric field concentrated on the tip end portion of the meniscus and, as shown in Fig. 5, becomes a chargedtoner group 10 containing the ink solution to fly toward the opposite electrode (not shown), i.e., the recording paper to thereby perform the recording. The toner sticking on the recording paper to form the recording dots is heated by a heater (not shown) and fixed. - On the other hand, the charge corresponding to the amount of charge held in the charged
toner group 10 which has flown is supplied to theink 9 in the vicinity of theink ejection part 5 from the portion which is not covered by the insulatinglayer 6 of therecording electrode 2. Thus, the electric balance is always kept. - As described above, according to the embodiment, since the
convex portion 12 of the cover member 4 on the ink ejection side is located at a position projecting beyond the tip end portion of thebase plate 1 in the ink ejection direction, theink meniscus 8 projects along theconvex portion 12 as shown in Fig. 5. Thus, the component in the tangent direction of the electric field with themeniscus 8 is toward the tip end of themeniscus 8 and its component becomes large. Accordingly, it is possible to rapidly supply the meniscus tip end portion with charged toner and to carry out high speed recording with high precision. - Also, the tip end portion of the cover member 4 is formed in the sawteeth, and the position of the
convex portion 12 for forming the sawteeth is overlapped with a line extending from thestylus recording electrode 2. As shown in Fig. 5, theink meniscus 8 has an apex corresponding to theconvex portion 12 of the cover member 4. For this reason, it is possible to more effectively concentrate the electric field diverging from therecording electrode 2 onto theconvex portion 12, and to rapidly carry out the supply of the charged toner to the tip end portion of the meniscus. At the same time, it is possible to carry out the high speed printing with high precision by using the plurality ofrecording electrodes 2. - Also, since the sawtoothed portion for concentration of the electric field is formed not on the
base plate 1 but on the cover member 4, it is possible to widen the variety of selection of the base plate material. Also, it is possible to widen the freedom of selection of the formation process for the recording electrode arranged on thebase plate 1 with high precision. As a result, by selecting the low cost material which would not be suitable in the conventional example due to the machining problem and using an easy process, it is possible to reduce the manufacture cost. Moreover, the thickness of the plate of the cover member 4 is made to one which is suitable for machining, it is possible to facilitate the machining of the sawtoothed portion, to thereby further reduce the manufacture cost. - Furthermore, since the cover member 4 is made of moldable material, it is possible to impart sufficient mechanical strength to the sawtoothed portion formed at the tip end portion on the ink ejection side. Thus, it is possible to prevent the damage of the sawtoothed irregularity portion due to the cleaning of the head tip portion and the clogging of the ports.
- Also, since the tip end portion of the
recording electrode 2 is covered by the insulatinglayer 6, the dielectric strength between therecording electrode 2 and the opposite electrode may be increased, and it is possible to effectively avoid such a disadvantage that an excessive current would flow due to the generation of jamming of the recording paper or the like to damage the drive device or the like. - In Fig. 4, the cover member 4 may be made of other material. Also, for the electrostatic ink-jet recording head in accordance with the embodiment, the insulating
layer 6 is formed after therecording electrode 2 has been printed first on the surface of thebase plate 1, and thereafter, the cover member 4 which is separately machined is mounted on thebase plate 1. Such an order of the manufacture process is preferable.
Claims (7)
- An electrostatic ink-jet recording head which uses ink containing color particle charged with a predetermined polarity, comprising a base plate (1), at least one recording electrode (2) formed on a surface of said base plate for generating an electric field for ink ejection; a cover member (4) for forming an ink flow path (3) in an ink ejection direction on the surface of said base plate where said recording electrode is formed; and an ink ejection port (5), formed in a tip end portion of said ink flow path, for ejecting the ink, characterized in that,
at least one convex portion (12) is formed at a tip end portion of said cover member and projects in the ink ejection direction, and said convex portion is set to project beyond a tip end portion of said base plate in the ink ejection direction. - The electrostatic ink-jet recording head according to claim 1, wherein said convex portion (12) has sharp-pointed end.
- The electrostatic ink-jet recording head according to claim 2, wherein a plurality of recording electrodes (2) are formed on the surface of said base plate and are arranged in parallel in a longitudinal direction along the ink ejection direction, and a sawtoothed portion is formed at the tip end of said cover member to form a plurality of convex portions (12), the convex portions being arranged so as to overlap on a line extending from the recording electrodes.
- The electrostatic ink-jet recording head according to claim 2, wherein said cover member (4) is made of moldable material.
- The electrostatic ink-jet recording head according to claim 2, wherein a tip end portion of said recording electrode (2) is covered by insulating material.
- The electrostatic ink-jet recording head according to claim 3, wherein said cover member (4) has path separators (4a) for separating the ink flow path (3), and said path separators are formed at positions where the recording electrodes (2) are partitioned.
- The electrostatic ink-jet recording head according to claim 2, wherein said ink ejection port (5) is formed by thickening the cover member to narrow the ink flow path.
Applications Claiming Priority (3)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
JP208863/95 | 1995-08-16 | ||
JP20886395 | 1995-08-16 | ||
JP20886395A JP2842318B2 (en) | 1995-08-16 | 1995-08-16 | Electrostatic ink jet recording head |
Publications (3)
Publication Number | Publication Date |
---|---|
EP0764529A2 true EP0764529A2 (en) | 1997-03-26 |
EP0764529A3 EP0764529A3 (en) | 1997-08-13 |
EP0764529B1 EP0764529B1 (en) | 1999-07-28 |
Family
ID=16563374
Family Applications (1)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
EP19960250175 Expired - Lifetime EP0764529B1 (en) | 1995-08-16 | 1996-08-15 | Electrostatic ink-jet recording head |
Country Status (3)
Country | Link |
---|---|
EP (1) | EP0764529B1 (en) |
JP (1) | JP2842318B2 (en) |
DE (1) | DE69603426T2 (en) |
Cited By (2)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
EP0869004A2 (en) * | 1997-04-04 | 1998-10-07 | Nec Corporation | Electrostatic ink-jet recording head |
EP1604825A1 (en) | 2004-05-18 | 2005-12-14 | Fuji Photo Film Co., Ltd. | Ink jet recording method |
Citations (3)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
JPS58179663A (en) * | 1982-04-14 | 1983-10-20 | Nippon Telegr & Teleph Corp <Ntt> | Ink recording head |
JPS60228162A (en) * | 1984-04-26 | 1985-11-13 | Tokyo Electric Co Ltd | Ink jet printer head |
WO1993011866A1 (en) * | 1991-12-18 | 1993-06-24 | Research Laboratories Of Australia Pty. Ltd. | Method and apparatus for the production of discrete agglomerations of particulate matter |
-
1995
- 1995-08-16 JP JP20886395A patent/JP2842318B2/en not_active Expired - Fee Related
-
1996
- 1996-08-15 DE DE1996603426 patent/DE69603426T2/en not_active Expired - Fee Related
- 1996-08-15 EP EP19960250175 patent/EP0764529B1/en not_active Expired - Lifetime
Patent Citations (3)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
JPS58179663A (en) * | 1982-04-14 | 1983-10-20 | Nippon Telegr & Teleph Corp <Ntt> | Ink recording head |
JPS60228162A (en) * | 1984-04-26 | 1985-11-13 | Tokyo Electric Co Ltd | Ink jet printer head |
WO1993011866A1 (en) * | 1991-12-18 | 1993-06-24 | Research Laboratories Of Australia Pty. Ltd. | Method and apparatus for the production of discrete agglomerations of particulate matter |
Non-Patent Citations (2)
Title |
---|
PATENT ABSTRACTS OF JAPAN vol. 008, no. 020 (M-271), 27 January 1984 & JP 58 179663 A (NIPPON DENSHIN DENWA KOSHA), 20 October 1983, * |
PATENT ABSTRACTS OF JAPAN vol. 010, no. 088 (M-467), 5 April 1986 & JP 60 228162 A (TOKYO DENKI KK), 13 November 1985, * |
Cited By (5)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
EP0869004A2 (en) * | 1997-04-04 | 1998-10-07 | Nec Corporation | Electrostatic ink-jet recording head |
EP0869004A3 (en) * | 1997-04-04 | 1999-09-15 | Nec Corporation | Electrostatic ink-jet recording head |
US6079817A (en) * | 1997-04-04 | 2000-06-27 | Nec Corporation | Electrostatic ink-jet recording head |
EP1604825A1 (en) | 2004-05-18 | 2005-12-14 | Fuji Photo Film Co., Ltd. | Ink jet recording method |
US7270400B2 (en) | 2004-05-18 | 2007-09-18 | Fujifilm Corporation | Ink jet recording method |
Also Published As
Publication number | Publication date |
---|---|
EP0764529B1 (en) | 1999-07-28 |
DE69603426T2 (en) | 2000-01-27 |
DE69603426D1 (en) | 1999-09-02 |
EP0764529A3 (en) | 1997-08-13 |
JP2842318B2 (en) | 1999-01-06 |
JPH0952366A (en) | 1997-02-25 |
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